Temporal trends in carbon cycling, leaf biochemistry and ecosystem function
Borden Forest Research Station - Centred on the flux tower at Borden Forest flux tower, Ontario, we have been involved in a number of projects aimed at better understanding and parameterising leaf pigment content and leaf nitrogen in leaf-canopy level photosynthetic processes, light use efficiency and their role in annual carbon budgets. Borden Forest is a mixed wood site, located in the temperate-boreal transition zone in Ontario and is the longest running operational flux tower in Canada; collecting eddy-covariance data since 1995. These continuous, high-frequency gas exchange measurements provide critical information on the relationships between environmental drivers and ecosystem function. For more information, please see: Froelich, N. Croft, H. et al. (2015) Trends of carbon, water and energy fluxes over a mixed temperate–boreal transition forest in southern Ontario, Canada. Agricultural and Forest Meteorology 211, 72-84 |
One of our key research questions has been centred around using novel remote sensing techniques to more explicitly represent the seasonal phenology of leaf physiology. Our research has demonstrated that there is a considerable temporal lag between budburst and leaf expansion, and chlorophyll development, using a combination of remote sensing data and laboratory analysis. Gas exchange and chlorophyll fluorescence measurements demonstrated that this lag in chlorophyll bioaccumulation reduces the photosynthetic rates of trees at the start of the season, even when the leaves are fully expanded. This decoupling of chlorophyll content and LAI has important implications for biogeochemical models that are reliant on LAI (or NDVI) and neglect the seasonality of leaf biochemistry, and has subsequently been demonstrated at local to global scales.
Croft, H. Chen, J.M. Froelich, N. Chen, B. and Staebler, R.M (2015) Seasonal controls of canopy chlorophyll content on forest carbon uptake: Implications for GPP modelling. Journal of Geophysical Research: Biogeosciences 120(8), 1576-1586
Luo, X.* Croft, H. Chen, J. He, L. Keenan, T. (2019) Improved estimates of global terrestrial photosynthesis using information on leaf chlorophyll content Global Change Biology 25(7), 2499-2514
Luo, X.* Croft. H. Chen, J.M. Bartlett, P. Staebler, R. Froelich, N. (2018) Incorporating leaf chlorophyll content into a two-leaf terrestrial biosphere model for estimating carbon and water fluxes at a forest site. Agricultural and Forest Meteorology 248, 156-168
Luo, X.* Croft, H. Chen, J. He, L. Keenan, T. (2019) Improved estimates of global terrestrial photosynthesis using information on leaf chlorophyll content Global Change Biology 25(7), 2499-2514
Luo, X.* Croft. H. Chen, J.M. Bartlett, P. Staebler, R. Froelich, N. (2018) Incorporating leaf chlorophyll content into a two-leaf terrestrial biosphere model for estimating carbon and water fluxes at a forest site. Agricultural and Forest Meteorology 248, 156-168